Circuit-arrangement for use in automatic telephone system



March 20, 1956 w. SIX ET AL 2,739,265

CIRCUIT-ARRANGEMENT FOR USE IN AUTOMATIC TELEPHONE SYSTEM Filed May 5, 1953 TORS JAG o a u s oomsune INVEN WILLEM SIX CIRCUIT-ANGEli-TENT FGR USE IN AUTOMATIC TELEPHGNE SYSTEM Willem Six and Jacobus Domhurg, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application May 5, 1953, Serial No. 353,112 Claims priority, application Netherlands May 5, 1952 3 Claims. (Cl. 315-84.5)

The invention relates to circuit-arrangements for use in automatic telephone systems.

Circuit-arrangements are known in which dial pulses are received in an electronic counting circuit. Such a counting circuit may, for example, comprise a number or" gas discharge systems which are ignited in succession by the dial pulses. In this case the gas discharge systems comprise a cathode, an anode and an ignition electrode and are furthermore constructed in a manner such that the anodes of the tubes are connected to a positive terminal of a voltage source, the cathodes through at least one resistor to a negative terminal of the voltage source and the ignition electrode of each subsequent system is connected to a point of the cathode lead of the preceding system. The tubes of the counting circuit are ignited in succession by the dial pulses, whereupon the counting circuit marks a definite outlet of a selector for establishing a desired connection in accordance with the numeral received. The counting circuit should not respond to a subsequent series of dial pulses, since in this case an unwanted connection would be established besids the connection already existing. The circuit-arrangement according to the invention obviates this difi'lculty.

The circuit-arrangement is characterized in that provision is made of an auxiliary gas discharge tube, an ignition electrode of which is connected to a point of the cathode circuit of the first tube of the counting circuit, this point being subjected to such a rise in voltage, when the first tube ignites, that the auxiliary tube can ignite. The auxiliary tube remains conductive during the call. A point of the anode lead of the auxiliary tube, including a resistor, is connected to the ignition electrode of the first tube of the counting circuit in a manner such that, if the auxiliary tube is conductive, the first tube of the counting circuit cannot ignite.

in order that the invention may be readily carried into effect, it will now be described in detail with reference to the accompanying drawing.

The drawing shows in a diagrannnatical, simplified form part of an electronic automatic telephone system, in which intelligence connections between the subscribers, for example, AA and AB, can be established by means of gas discharge tubes, for example BA and BB, which operate as electronic switching contacts, the control being carried out completely by electronic means. The apparatus of the subscriber AA is connected through the intelligence conductors S1 and S2 to ends of two identical windings of the transformer TA, associated with the line circuit LCA of the subscriber AA. The other ends of the said windings are connected to one another by a capacitor C12. and, moreover, by the interposition of a resistor R15, to difierent terminals of the battery BT. One end of a third winding of the transformer is connected to earth through a resistor Rza, shunted by a capacitor C22,, and the other end of this Winding is connected to the cathode k of the gas discharge tube BA. The anode a of tube BA is connected through the intellinitcd States Patent gence conductor S of the connecting circuit V0 to the multiple-Wire point P1, which is connected through an inductor L and the parallel combination of a resistor R1 and a capacitor C1 to a supply source V1, the voltage of which may, for example, be equal to v. with respect to earth. A first ignition electrode 1 of the gas discharge tube BA is connected to 21 tapping of a potentiometer RSa, R411 connected between earth and the junction P2 of the inductor and. the resistor R1. A second ignition electrode f2 is coupled through a delaying network, formed by resistors R511, R62., and capacitors C311 and C48,, with an outlet M2 of an electronic counting circuit TS, which is added to the connecting circuit VC and operates as a marking circuit. The multiple-wire point Qa is coupled in a similar manner by means of gas discharge tubes (not shown) with further connecting circuits. The line circuits of the other subscribers, for example, the line circuit LCB of subscriber AB, are arranged in a similar manner as the line circuit LCA.

The connecting circuit VC comprises a vacuum tube Bo and a plurality of gas discharge tubes B1 to B5 and the marking circuit TC comprises ten further gas discharge tubes, of which only tubes Be, B7 and B8 are shown in the drawing. Voltage variations at the multiplewire point P1 are amplified by tube. Bo and supplied with opposite polarity to a point U, from where they are transmitted through capacitors C10, C40, and C50 to gas discharge tubes B1, B4 and B5. The gasdischarge tubes B1 to B8 comprise each a cathode k, an anode a and an ignition electrode 1, as is shown for tube B1. The anodes of the tubes are fed by the supply source V1. The voltage of this source is lower than the ignition voltage between the anodes and the cathodes of the tubes; this ignition voltage is lower than v., but higher than the running voltage between the anode and the cathode which is 60 v. The resistor R11 in the anode circuit of tube B1 is shunted by a capacitor C11, so that this tube, after it has ignited, extinguishes automatically. For the same purpose, the resistors Ro and R51 in the cathode circuits of the tubes B4 and B5 are shunted by capacitors C41 and C51. In the rest position of the circuit-arrange ment all gas discharge tubes are extinguished.

Tube B4 serves to supply dial pulses to the marking circuit TS; these pulses ignite in succession one of the gas discharge tubes B6, B7, B8, and so on. When a subsequent tube of the marking circuit ignites, the preceding tube'extiuguishes. Tube 135 is intended to bring the marking circuit back into the rest position by extinguishing the tubes thereof. At the termination of the call the complete arrangement, including the tubes BA and BB, may be brought into the rest position under the control of the tubes Brand B2. The purpose of tube B; will be evident hereinafter.

The circuit-arrangement operates as follows. It is assumed that the subsrcibers AA and AB are marked by the numerals 2 and 3 respectively and that the sub scriber AA wants to establish a connection with the subscriber AB. When the subscriber AA lifts the receiver, the line loop is completed through the intelligence conductors S1 and S2 and the subscribers station, so that the transformer TA transmits a negative voltage pulse to the multiple-wire point Qt. The ignition electrode ii of the gas discharge tubes, the cathodes k of which are connected to point Q2. and the anodes a of which are connected to free-connecting circuits, are at a potential which is slightly lower than the ignition voltage between the ignition electrode f1 and the cathode k, so that, owing to the occurrence of the pulse at the cathode, all these tubes take up a position in which they are capable of igniting. As soon as one of these tubes, for example, tube BA, ignites, also the main discharge path between the cathode kand the anode 'a of this tube tube Ba is connected through the conductor M3 and the delaying network Rab, Rb, C4b and C3b to the ignition electrode f2 of the gas discharge tube BB of the line circuit of the wanted subscriber AB, marked by digit 3. Since after the third dial pulse no further pulses occur, the voltage at the said ignition electrode of tube BB can increase to the ignition value, so that tube BB ignites, if the subscriber AB is not engaged. At first it is assumed, however, that subscriber AB is engaged. One of the gas discharge tubes not shown, the cathode of which is connected to point Qb is then conductive and the voltage at point Qb is equal to 50 v. or 33 v. respectively according as the subscriber AB performs a call or is engaged in a call. If the voltage at the ignition electrode of tube BB has increased to the voltage at the cathode of tube Be, there is only a low voltage between the said ignition electrode f2 and the cathode k of tube BB, this voltage being lower than the ignition voltage, so that tube BB cannot ignite.

Then subscriber AA must receive a busy signal, which is supplied to him by the following circuit-arrangement: The busy-tone generator BG is connected through capacitor C2 to the tapping B of the potentiometer R3, R4, this tapping being connected through a rectifier G3 to the multiple-wire point P1 of the connecting circuit VC and through a rectifier G4 to the anode of tube B3. In the rest position of the circuit-arrangement the tubes, the anodes of which are connected to point P1, are not conductive, nor tube B3. The multiple-wire point P1 and the anode of tube B3 then have a voltage of 160 v. After subscriber AA has established a connection with the connecting circuit VC through tube BA, when making a call, the potential at multiple-wire point P1 drops to 110 v., whilst the anode of tube B3 maintains a voltage of 160 v., so that rectifier G4 is conductive and rectifier G3 is cut oif. The busy-tone generator BG cannot supply busy signals through capacitor C2 and rectifier G3 to the intelligence conductor S. After tube B3 has ignited at the first dial pulse, the voltage at the anode of this tube drops to 60 v., so that rectifier G is cut ofl. The point B of the potentiometer R3, R4 is chosen to be such that, if the rectifiers G3 and G4 are both cut ofi, point B has a voltage of 105 v. Consequently, when the rectifier G4 is cut oif, rectifier G becomes conductive, since point P1 has a voltage of 110 v. The busy-tone generator BG can thus supply busy-signal voltage through capacitor C2, rectifier G intelligence conductor S, the gas discharge tube BA and transformer TA to the station of subscriber AA. However, this subscriber cannot hear the busy tone in the receiver, since the apparatus is short-circuited during the dialling operation. After the dial has returned into the rest position, this short-circuit is eliminated and the subscriber receives busy-tone, if it is assumed, at least, that subscriber AB is engaged and the gas discharge tube BB does not ignite after the third dial pulse. If, after the call has not been replied to, the subscriber AA lays down the receiver, a strong positive pulse is produced by the interruption of the line loop across the windings of transformer TA, so that the potential of point Qa increases. In general this closing pulse is so strong that gas discharge tube BA extinguishes and a strong positive pulse is produced at point P1. If, owing to high line resistance, the pulse at point Qa is not sufiiciently strong to cause the tube BA to extinguish immediately, the tube transmits the pulse to point P1 so that also in this case a strong positive pulse occurs at point P1. The closing pulse is transmitted by tube B0 with opposite polarity to point U and supplied from there through capacitor C and rectifier G1 to the cathode of gas discharge tube B1. The ignition electrode 7 of tube B1 is connected to a source V3 of a voltage such that tube B1 ignites, if a strong negative pulse, as for example, occurs when the subscriber lays down the receiver, is supplied to the cathode, whereas it cannot ignite at a comparatively weak pulse, as for example occurs during a dial signal. Since the resistor in the cathode lead of tube B1 m'u'sthave a comparatively low value, in order to cause the tube to extinguish immediately after the ignition under the action of capacitor C11, the rectifier G2 is connected in series with resistor R12 in the cathode circuit; this rectifier has a polarity such that, when a negative pulse occurs at the cathode of tube B1, the rectifier is cut off and the pulse is not damped'by the low resistor R12. The'negative pulse increases the voltage between the ignition electrode and the cathode k of tube B1 and the tube ignites, so that the cathode voltage increases abruptly to a high value and the capacitor C20 transmits .a positive pulse to the ignition electrode of tube B2, which then ignites. At the same time rectifier G2 becomes conductive. The voltage at the anode of tube B2 drops abruptly from 160 v. to 60 v. and a strong negative pulse is transmitted through capacitor C21 and intelligence conductor S to the anode a of tube.BA, so that tube BA extinguishes and the connection between the line circuit LCA and the connecting circuit VC is interrupted. The negative pulse across the intelligence conductor S is reversed in polarity by tube Bo and supplied to point U, whilst at the same time the rectifier G1 and the capacitor C10 transmit a positive pulse directly from the cathode of tube B1 to point U.

These positive pulses ignite tube B4 and the counting circuit TS goes over in the manner described above into a subsequent position. In this case the positive pulse at point U is, however, so strong that also gas discharge tube B5 ignites. The resultant positive pulse at the cathode of tube B5 is transmitted through capacitor C52 and resistors R60, R70, R80, and so on to the cathodes of all tubes of the counting circuit, so that the ignited tube extinguishes. Tube B2 extinguishes automatically, owing to the provision of capacitor C21 in the anode circuit. Capacitor C12 transmits a negative pulse from the anode of tube B1 to the anode of tube B3, so that this tube also extinguishes. Thus the arrangement has returned into its rest position.

As stated above, when the subscriber AA makes a call, the potential at point P1 drops owing to the ignition of gas discharge tube BA. Tube Bo thus supplies a strong positive pulse to point U, so that gas discharge tube B4 ignites and tube B6 of the counting circuit also ignites in the manner described above, for the reception of the first dial pulse. The positive pulse at point U now is so strong that gas discharge tube B5 also ignites, so that tube Ba extinguishes immediately thereupon, as described above, before the gas discharge tube which couples the connecting circuit with the subscribers line circuit, corresponding to digit 1, can ignite. The rectifier G1 prevents the strong positive pulse at point U from being transmitted through capacitors C10 and C20 to the ignition electrode of tube B2. The pulse produced at point P1 in the event of a call, consequently, does not result, in contradistinction to dial pulses, in a permanent change in the state of ignition of the gas discharge tubes of the counting circuit TS.

It is now assumed that the suscriber called is not engaged. The ignition of gas discharge tube B8 causes tube BB to ignite, since the voltage at the cathode of this tube is now equal to earth potential. The current passing through the main discharge path between the anodes and the cathodes of the tubes BA and BB flows through resistor R1 and inductor L, so that point P1 assumes a potential of 93 v. and the multiple-wire points Qa and Qb in the line circuits LCA and LCB assume a voltage of 33 v. Owing to the decrease in potential at point P1 to 93 v., the rectifier G3 is cut off, whilst point B assumes a voltage or" v., since rectifier G4 is also cut oif, and the anode of tube B3 has a voltage of 60 v. Consequently, no busy tone is transmitted to the intelligence conductor S. The voltage of 33 v. at points On and Qb marks the line circuits LCA and LCB engaged, so that they can no longer be reached through another connecting circuit, as is set out above. Owing to the decrease in voltage at point P1, tube Bo transmits a positive pulse to point U, which causes the two tubes B4 and B5 to ignite, so that a subsequent tube in the. counting; circuit TS ignites, but immediately extinguishes, since; tube B- ignites. It. the line circuit LCB- is free, the counting circuit returns into the rest position, immediately after the numeral has been dialled. This isrequired: for an' additional reason, since, if the counting. circuit. would not extinguish until the call had terminated, the ignition electrode fa of tube BB- would maintain a comparatively high voltage for-a certain time, after all tubes of the: connecting circuit and tubes BB. and BA had extinguished, owing tothe. provision of capacitors Cars and C411, so. that tube BB could re-ignite.

When the subscriber AB- takes oil the receiver to respond to the call, the completion of. the line loop: produces; a. negative voltage pulse at point Qs, as in. the event ofi a call; the tube BB- transmits this, pulse. to point P1; and tube Bo. transmits it as a positive. pulse to point U. Tubes Br and B5 re-ignite and extinguish automatically without further efiect. Thus the desired. connection between the. subscribers AA and AB has. been established and: intelligence currents may be transmitted. in. both directions:

between the subscribers stations. through transformer TA, the main discharge path between the cathodes and the. anodes of tubes BA and BB and transformer-TB,

It at the tern'iinatiorr of the call one of thev subscribers: lays down the receiver, a. strong positive closure. pulse is transmitted to point P1, so. that in the manner described: above the gas discharge tubes BA and BB extinguish, similarly to tube B3, which remains conductive: during the call. Thus the complete arrangement has returned: into the rest position. When the second subscriber also. lays: down the receiver, for example, subscriber AB, a positive pulse is produced at point (It, the polarity of this pulse, however, is such that tube BB cannot re-i'gnite.

if during the call one of the subscribers would dial again a numeral, the counting circuit would again record this numeral in the manner described above, so that an undesirable communication with another subscribers line would be established. Such a situation may also occur, if not a subscribers line, but a selector of a subsequent selection stage would be connected to the windings of transformer TB; this selector would have tobe: adjusted by a subsequent pulse series. Also in this case the counting circuit must not re-ignite, after the numeral has. once been dialled. This is prevented by the provision oftube B3. As: stated above, tube B3 ignites: at the. first pulse of the first pulse series and remains conductive till the termination of the call. The anode of tube B; then. has a voltage of 60-v., so that point A has a voltage which is comparativelyfar less than. the ignition voltage of. the gas discharge tubes, so thattube Be cannot re-ignite when tube 34- ignites.

What is claimed is:

l. A circuit-arrangement in an automatic telephone system comprising a counting circuit including a plureality of successively arranged gas discharge tubes, each of said tubes having a cathode, an anode and an ignition electrode, eachof said anodes being connected to'a positive terminal of a source of potential, the: ignition electrode. or each succeeding tube of said plurality'of tubes being coupled to the cathode of each preceding tube,

means tor interccupling said cathodes, a pluraIit-y of resistors, each of said resistors: being interposed between one of said cathodes and a negative terminal of said source: of potential, means for applying dial pulses to 8 said counting, circuit, an auxiliary gas discharge tube having an ignition. electrode and ananode, said ignition electrode being connectedto the cathode of the first tube. of. said: plurality of successively arranged tubes in a mannensuchthat when said. first tube ignites, a voltage increase at. said first tube cathode ignites said auxiliarytube, and ananode resistor coupling the anode of said auxiliary tube to the ignition electrode. oil said first tube in. a manner suchv that ignition or said first tube is. preventedv during. the conduction ofsaid auxiliary tube.

2.. A circuit-arrangement in an automatic telephone. system comprising acounting, circuit including; a plurality of successively arranged gas discharge tubes, each of. saidtubes having a cathode, an anode and an ignition. electrode, said anodes being connected to a positive terminal of a source ofi potential, the. ignition; electrode. of each succeeding tube of said plurality of tubes being coupled to the cathode. of eachpreceding; tube, a. plurality ofv capacitors, each of said capacitors intercoupling two successive cathodes of; said. plurality Of: tubes, a plurality of resistors, each of said resistors being. interposed between one of said cathodes. and a negative terminal. of. said source. of potential, means for applying dial pulses to the ignition electrodes ofi said. tubes, an. auxiilary gas discharge tube having an. ignition electrode and an anode, said ignition electrode being connected to the cathode of the first tube of said plurality of successively arranged tubes. in a manner. such that when said first tube. ignites,v a! voltage increase atv saidfirst tube cathode ignites said auxiliary tube; and an anode resistor coupling the anode of said auxiliary tube to the ignition electrode of said first tube in. a manner such that ignition of said first tube is prevented during theconductioir of said auxiliary tube.

3.. A circuit-arrangement in an. automatic telephone system comprising acountingv circuit. including a plurality of successively arranged. gas discharge tubes,.each oi said tubes having a cathode, an anode and an ignition electrode, said anodes being, connected to-a positive. terminal of. a. source of. potential, the ignition. electrode of eachsucceeding, tube. of said plurality 0t tubes being coupled to the. cathode. of each preceding tube, a. plurality of capacitors, each of said capacitors intercoupling two sue.- cessi've cathodes 015 said plurality oftubes, a plurality of resistors, each of said. resistors being interposed between one of said cathodes. and. a. negative. terminal. of said source of potential, means for applying dial pulses to the ignition electrodes of said. tubes, an. auxiliary gas discharge tube having. an ignition electrode and an anode, said ignition electrode being connected to. the oathode. of the first tube of said plurality of succesively arranged tuhes in a manner such that. when said first tube. ignites, a voltage increase at. said first tube cathode ignites said auxiliary tube, a first anode resistor interposed between said auxiliary tube anode and said negative terminal', a second anode resistor interposed between said auxiliary tube anode andsaidpositiveterminal, and means for coupling a point on said. first anode resistor to the ignition el'ectrodeof said first tubein a manner such that ignition of said; firsttube is prevented during the conduction of said auxiliary tube.

References: (Iited in the file of this patent UNIT ED STATES PATENTS 

